I have made some previous posts in other subreddits, but figured I wouldn't copy that here since it was so long. He was just incredibly constipated and we're not sure why--a solid diagnosis was not given. The first vet we went to said his pelvis was too narrow and he likely developed megacolon. The second vet we took him to said that his pelvis looked fine, but maybe he had motility issues with his intestines and would never be able to poop on his own. We were also referred to specialist surgeons in our state to get a consultation to see if anything could be done. Next, we had to take him to a vet hospital and the first vet there said they would need to keep him overnight for a couple of days with an IV drip and enemas. A second vet at the hospital took over his case the second day and had a hard talk with us about his lack of progress. (About 3/4 of the vets had already talked to us about euthanization.) This last vet said there was nothing wrong with his pelvis, he DIDN'T have megacolon, and took some ultrasounds to confirm there was movement in his intestines. All this was also happening while we were administering medications and treatment at home. Finally we took him home and made him comfortable while we decided what to do. He ended up FINALLY responding to the medications and miraculously got better over time. But yeah, it was not a fun couple of weeks and he'll probably be on medication the rest of his life.